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Bovine TB Control in Great Britain A Paper for Discussion

by the National Beef Association can be seen in full here pdf file

It makes 18 recommendations, including "the obvious potential of a portable PCR cycler machine" (See below)

NBA recommendations for TB control:

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1. Bovine TB is increasingly expensive both to Government and industry but it is a case where front-loading of cost will undoubtedly save money in the long run so long as a full basket of control measures is implemented. This needs to be properly explained to Treasury.

2. To bring a disease under control it is imperative that one knows where it is. The inspection for bovine TB lesions in OTM carcases, a major element in surveillance for bovine TB, may be too hurried to be effective. It is recommended that more care is taken and a sample of culls from herds with repeated TB reinfections are examined with closer veterinary attention, if necessary growing cultures from tissue samples of any carcase under suspicion.

(Only 154 cattle with visible lesions at inspection out of 3.4 million carcases seems to be almost too good to be true.)

3. Conduct a full analysis of the DEFRA database and link its information to industry databases to construct a clear national, regional and farm cluster (not merely parish) description of the incidence of TB nationwide. Faster analysis of TB 99 information would assist in compiling this essential instrument of control.

In many cases TB restrictions on neighbouring farms are completely anomalous merely because they are in adjoining parishes.

4. Test all herds in parishes within 30 kilometres of any TB incident on an annual basis until that parish has been clear of TB for at least 3 years.

5. Treat any new TB out-breaks in TB clean areas urgently by testing cattle on all neighbouring farms twice, firstly within two months and then a second time after a 60 day interval. Test sufficient of the local badger population to establish whether the TB flare-up is badger derived or cattle to cattle infection or from some other cause. Such testing could use the PCR method described in 4 (c).

6. In any case immediately introduce field trials on the portable PCR machine described in section 4 (c) of this paper for both badgers and cattle.

7. The NBA would support a blitz on cattle TB using both the skin test and the GI blood test (subject to the comments in section 4 (b)) in repeat TB incidents in low risk areas.

8. The rescheduling of testing areas i.e. six months, one, two and three years using specifically targeted areas or farm clusters rather than parishes, is necessary (see recommendation 3 above).

9. Continue enforcement of test intervals.

10. Where practicable, farmers should maintain records of where individual animals (within groups) have grazed over the summer months – particularly if they have been in fields close to badger setts or fields in which badgers are regularly present. This could provide data valuable to the understanding of local patterns of infection.

11. Reduce TB spread into low risk areas by post-movement isolation and double testing of all cattle carried from high risk to low risk regions. Where SVS veterinary inspection justifies it, cattle housed in isolation from breeding animals and going for slaughter before turn-out, could be put lower on the priority list and might often be slaughtered before a second test.

12. Any translocation of badgers from one area to another (except by DEFRA officials) should be made illegal. All badger sanctuaries should be licensed, regularly inspected, and should have to keep full records of all badgers in their care.

13. Expand the RTA survey of dead badgers throughout all high risk areas and for at least 150 kilometres beyond these. Indicate to farmers where the badger population remains free of infectious TB so they can be reassured that their local badger population is keeping outside badgers at bay. Where TB-infectious badgers are found, employ an experienced local wildlife watcher (such as a gamekeeper) to carry out an urgent survey of the numbers of badgers per sett within the locality to see the extent to which these exceed 8 per sett and to note the number of main setts in a given area.

14. Krebs reactive trial areas (now only being "observed") should be treated as proactive areas. This should be done to reverse the 27% average increase (compared to the control areas) in TB herd breakdowns caused by the (often much delayed) reactive culls. Now that the main trapping has been done in the proactive areas the DEFRA badger trapping teams can be spread wider.

15. DEFRA must remove the current moratorium on its use of section 10 of the 1992 Protection of Badgers Act which provides for licences to be granted for the removal of badgers for the purpose of preventing the spread of disease, serious damage to land, crops, poultry or any other form of property. This will open the way for limited and targeted removal of badgers under full DEFRA control, with the option for them to check such badgers to ascertain the extent of TB infection.

16. Once the effectiveness of the Krebs proactive treatment is proven, roll this outwards into adjoining TB-infected badger areas and catch any new spread of TB in badgers into lower risk areas. It should be remembered that when the 10 Krebs trial areas were chosen, they covered 75% of the TB restricted areas of the country. They now only represent about 12% of the TB restricted farms. I

17. Subject to the result of the field trials in 4 (c) (PCR testing) ensure that, where TB infected badgers are found within the Krebs trial proactive areas, and in danger spots in clean areas, the infected setts and their social groups are treated with carbon monoxide, and the setts filled in, to eliminate spread of infection to healthy badgers moving inwards. This task should be done working inwards from the outer ring to reduce the risk of infected badgers moving outwards to a clean area. See end note v

18. Publicise through all possible means:

a) The reasons why some badgers need to be culled. Include photographs of emaciated badgers in the final stages of death from TB and of their internal organs post mortem

b) The use of the PCR technique to differentiate between infectious badgers and the rest.

c) The fact that the skin test on cattle is close to 100% effective when repeated at a 60-day interval.

d) The fact that the normal incidence of TB in a herd shows that only a very few cattle have been infected (often only one and more often under 5 in 1,000 cattle), and that farming methods are therefore unlikely to be the prime cause of escalating bovine TB.

e) That the so-called 'bio-security' of attempting to separate badgers from cattle is wholly impractical.

f) The high cost of TB control and the rate at which TB costs are escalating.

g) The fact that bovine tuberculosis can be transmitted to people (children in particular), and pets, from badgers’ urine, pus or sputum, and that both people and other animals are in at greater risk because of the seven-fold increase in these sources of infection.


(page 10 of pdf file)

PCR (Polymerase Chain Reaction)

There are two forms of using this powerful technique by which an enzyme and a cycle of heating and cooling is used to generate billions of copies of segments of DNA (to make detection and spoligotyping easier). After multiplication, the system identifies TB, or any other bacteria, or virus or DNA material by comparison with a known sample, utilising the properties of florescent light to do so.

a. Laboratory-based conventional heating block thermocycler using agra gel electrophosesis; this has greatly facilitated research in the Badger Road Traffic Accident study.

b. A portable mini-lab which can give an on-the-spot diagnosis of infection within 30 minutes; this technique has been developed for detection of biological warfare agents on the battlefield in the US, and in this country by the Defence Science and Technology Laboratory. In the UK it is being "spun-out" by an offshoot of the MOD, Enigma Diagnostics, with investment led by Porton Capital, and including the Treasury and a private venture company, Partnerships UK, and was announced in the veterinary press in September. I

A variant of this system in the form of a machine called a Lightcycler, was recommended by Professor Fred Brown of the US Plum Island Animal Disease Research Center in 2001 to the UK Government to rapidly diagnose Foot and Mouth on site. One individual went as far as ordering one, at a cost of £20,000, but the Government intervened to prevent this without providing the industry or even the individual with an explanation.

I Veterinary Times 27th Sept '04 "Battlefield technology deployed in fight against bovine TB" and BBC News 4th Oct '04
The obvious potential of a portable PCR cycler machine is to give a rapid identification of TB and the spoligotype of TB present in badgers. If one animal from a sett is found to have TB of a type causing infection in nearby cattle, then that sett could be treated with carbon monoxide with less nervousness by Ministers who would be able to give a better explanation to the general public.

There are 29 strains or spoligotypes of bovine TB, of which 17 are found very infrequently. In the UK the most common is type 9 with type 11 being more common in Devon, type 21 and 9 more common in Somerset and Dorset, and Cornwall being higher in types 9 and 15. The geographical distribution of spoligotypes of bovine TB in badgers has a high level of correlation with the distribution of spoligotypes in cattle. Spoligotype 35 has recently been identified in farmed deer near Ulverston, Cumbria, and linked to a spread to cattle there. The samples for multiplication in the PCR machine can be from any source and could merely be from a small amount of cattle blood or badger sputum or urine. Samples from several animals can be put in each of the glass testing tubes within the machine. A single case of infection in one animal would show up, allowing immediate rechecking of the animals in that batch.

The suitability of the portable PCR cycler machine for testing cattle for TB obviously depends on finding cattle that are shedding TB bacilli - either in milk, saliva, dung or urine - or which have bacilli in their blood.

The potential advantages of the PCR cycler over the gamma interferon test is that it should be able to differentiate between bovine TB and avian TB in blood and can be used on farm and give a result within 30 minutes. In the case of cattle this would save the wait of 3 days to read the skin test and the further wait of 6 to 12 weeks for confirmation of TB by culture test.

However the PCR cycle seems potentially to be of even more use in identifying bovine TB in badgers - which no other test can currently do satisfactorily. The sensitivity of the current (brock) ELISA blood test for badgers is only 40.7 per cent, and needs to be done 3 times at 28 to 42 day intervals, which entails keeping wild badgers in captivity for at least 84 days for a result. I

A further attraction of using this PCR technique is that it may be accurate enough to distinguish the TB status of individual badgers within a sett. If a half hour test can reveal this, then the targeted cull of badgers that we propose might be refined even further.